The present invention relates to an arrangement used in a system with a range of dental screws for tightening the screws by means of one and the same screw tightener or screwdriver, which screws in this case consist of different types and have different constructions in terms of screwhead height, screw length, thread diameter, etc. Each screw in this case has an internal recess via which the cooperation with the screw tightener is afforded. Each recess has elements extending inwards towards the centre axis of each screw, and the screw tightener has, at its end which can cooperate with the screws, parts which can cooperate with the elements during screw tightening. The said elements in each recess extend, in the longitudinal direction of the recess, essentially parallel to the longitudinal axis of the screw. The invention also relates to a range of dental screws.
It is known that in the case of high turning moments, the tightener or screwdriver must be deeply engaged in the screwhead so that the contact surfaces between the screw and the tightener are large. It is also known that in the case of dental products there is a requirement to be able to transport the screw in question, held on the tip of the tightener or screwdriver, without any risk of the screw falling off. It has hitherto been proposed, inter alia, to provide each screwhead with internal elastic elements arranged at or in the recess in order to ensure the said bearing capacity function. It has also been proposed to make available a relatively large number of different tighteners or screwdrivers which are intended to match a small number of screws. This has led to a high degree of complexity in the system for application of implants.
There is general interest in reducing the number of different instruments which need to be used in the application of dental implants. There is therefore a requirement for one and the same tightener or screwdriver to be able to be used for a large number of different screws. Likewise, it must also be possible to satisfy the requirement for the smallest possible dimensions.
There is also a requirement for the screws and/or the screwdriver to be able to be produced in a conventional manner, without using elastic elements, O-rings or the like.
The object of the invention is to solve the above problems, inter alia, and it proposes new ways of creating effective driving and bearing capacity functions in this context. In the case of high driving moments, a large degree of penetration of the tightener into the respective screwhead is required, and the invention is based on the recognition that the height of the screwhead or the depth of the recess must be set in relation to the driving moment requirement, while at the same time satisfying the bearing capacity function. The invention solves this problem too by proposing an arrangement in which the number of tighteners or screwdrivers is balanced against the requirements regarding tightening moment and the desire for the smallest possible dimensions.
There is also a requirement to keep down the costs of manufacturing the screw range. The invention solves this problem too.
The feature which is principally regarded as characterizing an arrangement according to the invention is that the circular cross-section of the screw tightener, at the outsides of the said parts, widens slightly conically from the said end, at the same time as the surfaces of the parts bearing against the elements are essentially parallel to corresponding surfaces of the elements.
In one embodiment, the invention is characterized by the fact that the recesses in the screws operated by the tightener are adapted, in accordance with each tightening moment effected by the tightener, by selecting different screwhead heights and on the basis that the smallest possible dimensions are to be retained. A bearing capacity or firm wedging required between the tightener and the respective screw is also provided in this case.
An alternative way of looking at the invention shows that it can be characterized by the fact that the tightener and the screws work with two functions, where the first function is a tightening function and the second function is a bearing capacity function consisting of a firm wedging occurring between the tightener and each screw when the tightener is introduced into the recess of the screw, and that the first and second functions are in this case mechanically separate.
In further developments of the inventive concept, it is proposed that by selecting larger recesses, the tightener is able to penetrate deeper down into each recess, and vice versa. In one embodiment, the recesses of the screws are selected with increasing diameter values seen across the whole range, and the increasing values meet increasing requirements of high turning moments, and vice versa. In one embodiment, the height of the screwheads is set in relation to the driving and bearing capacity functions, so that higher screwhead heights are used for greater driving force, and vice versa, the bearing capacity being effected by the cooperation between the screwdriver and the screw material at the mouth of each recess, so that the required bearing capacity is present independently of the height of the screwhead.
A range of dental screws is characterized, inter alia, by the fact that each screw is arranged to cooperate with a screw tightener whose circular cross-section, at the outsides of the parts, widens slightly conically from the end. Also present on the elements there are cooperating surfaces which are essentially parallel to corresponding cooperating surfaces on the parts of the screw tightener. The range can also be characterized, inter alia, by the fact that each screw is arranged for two functions, namely a tightening function and a bearing capacity function, which functions are mechanically separate.
Further characteristics and developments are evident from the subclaims which follow. Thus, for example, the screw diameters are selected in the range from 1 to 3 millimeters, preferably from 1.4 to 2.5 millimeters.
A great benfit is gained by virtue of the fact that the number of tighteners or screwdrivers can be reduced for the same number of different screws. The manufacturing accuracy or the tolerances are adapted to the driving and bearing capacity requirements, which affords advantages from the manufacturing and cost aspects seen across the whole range. The invention is based on the use of tighteners of the screwdriver type, but the screws in question can also be operated using conventional hexagonal drivers (multi-edge drivers).